Field of the Invention
The present invention relates to a method for manufacturing a resist composition to be used in fine processing in a process for manufacturing a semiconductor apparatus including a semiconductor device, etc., in particular, a composition for a resist film to be used in the multilayer resist method.
Description of the Related Art
Accompanying with high integration and high speed acceleration of an LSI, miniaturization of a circuit pattern size is rapidly progressing. The lithography technology has achieved formation of a fine pattern by shortening wavelength of the light source and selecting an appropriate resist composition thereto, which are to conform to the miniaturization.
However, in the case where miniaturization is performed with the same light source, when the miniaturization is performed with the same film thickness of the photoresist film to be used, i.e., when a pattern width is made smaller, the aspect ratio of the photoresist pattern after development becomes large, and pattern collapse occurs as a result. Thus, the photoresist film thickness has been thinned accompanied by the miniaturization so that the aspect ratio of the photoresist pattern is in an appropriate range. However, due to thinning of the photoresist film, the problem further generated that precision of pattern transfer to a substrate to be processed is lowered.
As one of the methods to solve the above-mentioned problems, there is a multilayer resist method. In this method, an under layer film having etching selectivity different from that of a photoresist film, i.e., a resist upper layer film, is interposed between the resist upper layer film and a substrate to be processed, then a pattern is formed at the resist upper layer film, then the pattern is transferred to the under layer film by etching using the upper layer resist pattern as an etching mask, and further the pattern is transferred to the substrate to be processed by etching using the under layer film as an etching mask.
As the resist under layer film used in the multilayer resist method, a silicon-containing resist under layer film has been used in recent years (Patent Document 1). This silicon-containing resist under layer film is easy in forming a film, and has an etching selectivity different from that of an upper layer resist, so that it is excellent in processing performance. On the other hand, a composition for forming the silicon-containing resist under layer film is different from an organic film material which does not contain silicon such as the conventional photoresist material, etc., and once it begins condensation of the polymer and becomes a higher molecular weight polymer in a pipe or in a filter, a solvent-insoluble deposit is generated. This is a property of a silicon-containing polymer contained in the composition for forming the silicon-containing resist under layer film. The deposit of the polymer is in generally called as a siloxane gel, a size of which is extremely small, so that it passes even a filter having a pore size of 20 nm or so, which is connected to a discharge pipe of a coating apparatus for forming a silicon-containing film, and observed as defects in a silicon-containing coating film formed on a substrate for manufacturing a semiconductor apparatus.
The defects in the coating film are minute unevenness generated when a resist composition is coated on a substrate for manufacturing a semiconductor apparatus, and defects contained in the resist film, in particular, in the silicon-containing resist under layer film, affect the pattern of the resist upper layer film, which cause pattern defects in many cases. When the pattern defects are transferred to the substrate to be processed for a semiconductor apparatus by dry etching, the manufactured semiconductor apparatus shows electrical abnormality such as open abnormality, short-circuit abnormality, etc., in the circuit, which is one of the reasons in lowering yield of the semiconductor apparatus. At present, the method for effectively removing the siloxane gel generated in a pipe or in a filter is limited only to filtrate the gel using a filter, which is not sufficient for removing particularly small defects, so that an effective means is being required.